Explants of porcine endometrium will be maintained in organ culture for periods up to one month in presence of radio-labeled amino acids and precursors of glycoproteins. The effects of a variety of hormones, particularly progesterone, estrogens and growth hormone on the secretion of uterine specific macromolecules will be investigated. Products are detected by two-dimensional electrophoresis and autoradiography of dried gels, or by immunological procedures. The uterine-specific purple protein can also be recognized by its acid phosphatase activity. We are using in vitro culture techniques to study the growth and metabolic activity of the elongating blastocyst in presence of either whole uterine secretions, cultured endometrial explants or cell cultures derived from the uterine epithelium. Finally, we are attempting to manipulate the culture conditions for growing uterine epithelial cells in such a manner that the cells begin to secrete significant quantities of purple protein into the medium.